Abstract: The present invention discloses a pin-on-disk type in-situ current-carrying friction testing system, and belongs to the technical field of friction performance testing. The friction testing system includes a pin-on-disk type friction pair, a current loading mechanism, and a magnetic field generating mechanism. The current loading mechanism includes a conductive terminal abutting against an annular sidewall of a disk specimen and used to guide a current in the disk specimen to flow along a horizontal direction, and the magnetic field generating mechanism is used to generate a magnetic field. When a pin specimen and a disk specimen rotate relatively, the pin specimen, the conductive terminal, and the magnetic field generating mechanism are relatively stationary, and an Ampere force generated by the current in the disk specimen flowing in the horizontal direction under the action of the magnetic field faces a support platform.

Abstract: A system and method for performing structural health monitoring on a structural element while it remains in service and experiences normal loading. The energy input to the element will be the normal and random energy inputs the element sees in service. The inventive system places an intelligent module at one or more points along the length of the structural element. The inventive system collects mass data from multiple modules on multiple elements. The system then applies machine learning or artificial intelligence techniques to detect changes in the measurements received from one or more modules. This approach reduces or eliminates the need to provide calibrated input energy. The invention preferably provides the ability to determine the condition of one element or sub-element under measurement relative to other elements.

Abstract: An optical fiber ring interferometer is provided, which is based on a common light path for two or more light beam pairs preferably originated from two or more light sources of a substantially different spectrum or from a single light source split spectrum and whereas each light beam of a specific pair is propagating in relative opposite directions, wherein at least one pair of light beams is utilized to detect acousto-mechanical events and to provide information regarding location and other characteristics of detected environmental disturbance.

Abstract: An optical signal receivers, systems including the optical signal receivers, and methods of operating the same include a multimode fiber circulator including a first port, a second port, and a third port, a first multimode fiber cable coupled to the first port and having an input configured to receive a complex modulated optical signal and provide the complex modulated optical signal to the first port of the multimode fiber circulator, a second multimode fiber cable including a low Q optical resonator coupled to the second port of the multimode fiber circulator that is configured to receive the complex modulated optical signal from the second port of the multimode circulator, and a third multimode fiber cable coupled to the third port of the multimode fiber circulator that is configured to receive a reflected optical signal from the third port of the multimode circulator, the reflected optical signal being reflected from the low Q optical resonator.

Abstract: The disclosure relates to a method for fabricating a speckle for high temperature deformation measurement of a shaped refractory material. A technical solution includes mixing a hercynite micropowder and a liquid mixing agent in a mass ratio of (3-6):1, and ultrasonically treating to obtain a speckle mixture; polishing a surface of a shaped refractory material to be measured, removing impurities, and spraying the speckle mixture on the surface of the shaped refractory material to be measured with a pneumatic airbrush in a time hood to obtain an uncured speckle; heating the uncured speckle to 60-80° C., keeping for 1-3 h, then heating to 100-120° C., and keeping for 1-3 h to obtain a speckle for high temperature deformation measurement of a shaped refractory material. The fabricated product is suitable for high temperature deformation measurement of a shaped refractory material at 1,600° C.

Abstract: A defect inspection apparatus (100) is provided with and an excitation unit (1) for exciting elastic waves, an irradiation unit (2) for emitting laser light, a measurement unit (3) for measuring interference light, and a control unit (4). The control unit is configured to acquire an image (61) representing a vibration state of an inspection target object (7) in a measurement area based on a measurement result of the measurement unit (3), detect a discontinuous portion in a vibration state in the measurement area from the image representing the vibration state as a defect (73), and identify a type of the defect based on at least one of a shape (62) of the detected defect and the vibration state of a defective portion.

Abstract: A method of performing an automated non-destructive examination of a composite structure includes identifying surface damage on the composite structure, coupling an automated tap tester device to a surface of the composite structure at a location of the surface damage, and performing, with the automated tap tester device, a plurality of tapping impacts on the surface within a testing area that encapsulates the surface damage. The method also includes receiving a plurality of acoustic signals associated with the plurality of tapping impacts, modeling sub-surface damage associated with the surface damage based on an analysis of the plurality of acoustic signals.

Abstract: Apparatus and associated methods relate to determining the wavelength of a narrow-band light beam. The narrow-band light beam is passed through an optical filter. The optical filter has complementary and monotonically-varying transmission and reflection coefficients within a predetermined band of wavelengths. The predetermined band of wavelengths includes the wavelength of the narrow-band light beam. A first photodetector detects amplitude of a first portion of the narrow-band light beam transmitted by the optical filter. A second photodetector detects amplitude of a second portion of the narrow-band light beam reflected by the optical filter. The wavelength of the narrow-band light beam is determined, based on a ratio of the determined amplitudes of the first and second portions of the narrow-band light beam transmitted and reflected, respectively.

Abstract: A shearography a system and method for regularizing phase resolved shearograms with an arctan regularization function to produce regularized phase resolved shearogram outputs is provided. The system and method of the present disclosure optimizes the processing of phase resolved shearography allowing interference fringe analysis techniques to be applied to the regularized phase resolved shearogram output results of the processing.

Abstract: Devices, systems and methods for optical spectroscopy using a Fourier transform that improve measurement speed, and relax the sampling rate and dynamic range requirements compared to conventional techniques, are described. One exemplary method for optical Fourier transform spectroscopy includes receiving a broadband signal, spectrally partitioning the broadband signal to generate a plurality of spectral channel interferograms, computing a one-dimensional Fourier transform of a function of each of the plurality of spectral channel interferograms to generate each of a plurality of channel spectrums, and reconstructing a spectrum of the broadband signal based on the plurality of channel spectrums. Embodiments of the disclosed technology include a free-space channel dispersed Fourier transform spectrometer and an integrated silicon-on-insulator Fourier transform spectrometer.

Abstract: A design of an integrated computational element (ICE) includes specification of a substrate and a plurality of layers, their respective constitutive materials, target thicknesses and refractive indices, where refractive indices of respective materials of adjacent layers are different from each other, and a notional ICE fabricated in accordance with the ICE design is related to a characteristic of a sample. One or more layers of the plurality of layers of an ICE are formed based on the ICE design, such that the formed layer(s) includes(e) corresponding material(s) from among the specified constitutive materials of the ICE. Characteristics of probe-light interacted with the formed layer(s) are measured at two or more temperatures. Temperature dependence(ies) of one or more refractive indices of the corresponding material(s) of the formed layers is(are) determined using the measured characteristics.

Abstract: Embodiments described herein may be applied to monitoring and evaluating rocket engine and other reusable components' health by tracking full-field stochastic patterns using Digital Image Correlation (DIC) to detect deformation. In particular, rocket engine cylindricity enables pre-flight and post-flight non-destructive inspection utilizing a turntable to detect local fatigue. In accordance with embodiments of the present disclosure, a rocket engine may undergo a DIC process, where the rocket engine is rotated via a turntable. Accordingly, the use of a turntable allows a single camera DIC setup to acquire data indicative surface measurements about the entire rocket engine. The rocket engine may then be flown and subsequently recovered. After recovery, the rocket engine again may undergo DIC processing, where the rocket engine is rotated via the turntable. The pre- and post-flight data may be compared to provide evidence of the existence of a deformation or lack thereof.

Abstract: A hose to be evaluated is installed on a fixing frame in a preset shape, and a strain gauge and markers are attached to a surface of the hose. During a course of application of predetermined internal pressure to the hose, strain data is acquired using the strain gauge and an image of an external shape of the hose is captured using a camera device to acquire image data. Based on the strain data and the image data acquired, a change in the shape of the hose between a plurality of time points at identical internal pressure is determined. Such hose fatigue resistance evaluation system can determine changes in the degree of deformation of a hose over time due to repeated application of internal pressure.

Abstract: A method of inspecting a secondary bond of a laminated part includes positioning the laminated part within a sealed chamber. The method also includes reducing a pressure within the sealed chamber to below a pressure outside the sealed chamber when the laminated part is positioned within the sealed chamber. The method further includes, when the pressure within the sealed chamber is reduced to below the pressure outside the sealed chamber, measuring a gradient of change of a surface profile of the laminated part. The method additionally includes determining a condition of the secondary bond based on the gradient of change of the surface profile of the laminated part.

Abstract: The subject matter of this specification can be embodied in, among other things, a method that includes separating, from a few mode optical fiber, a collection of backscattered Rayleigh signals based on a vibration of the few mode optical fiber at a vibration frequency at a first location along the few mode optical fiber, separating, from the few mode optical fiber, a collection of backscattered Stokes Raman signals and Anti-Stokes Raman signals based on a temperature of the few mode optical fiber at a second location along the few mode optical fiber, detecting the separated Rayleigh signals and Raman signals, determining, based on detecting the collection of backscattered Rayleigh traces, at least one of the first location, the vibration frequency, and an amplitude of the vibration, and determining, based on the detecting the collection of backscattered Raman signals, the temperature at the second location.

Abstract: The present invention discloses a Fiber Bragg Grating demodulation device with a suppressed fluctuation at a variable ambient temperature and a demodulation method. The device comprises a broadband light source (1), an optical attenuator (2), a tunable F-P filter (3), a first optical fiber isolator (41), an erbium-doped optical fiber amplifier (5), an optical fiber first-stage beam splitter (6), a first optical fiber second-stage beam splitter (71), optical fiber circulators (8), FBG sensor arrays (9), a first photoelectric detector array (161), an optical fiber gas cell (10), a second optical fiber second-stage beam splitter (72), an optical fiber F-P etalon (11), a notch filter (12), an optical fiber assisted interferometer (13), a data acquisition card (17) and a processor (18).

Abstract: A Pulsed Thermography (PT) system and method is provided utilizing a long duration pulse in combination with a radiant heat shield as a non-destructive testing method for quantitatively measuring defect depths within a 3D printed part and for characterizing layer-by-layer surface defects in the 3D printed part.

Abstract: An apparatus for locating a measurand anomaly, such as a hot-spot, along an optical waveguide is provided having: an optical waveguide, a light source configured to transmit light along the waveguide and a plurality of sensors provided along the waveguide. Each sensor is configured to reflect a portion of light propagating along the waveguide at a respective sensor wavelength corresponding to a measurand. The plurality of sensors is configured into one or more sets according to their sensor wavelengths, each set comprising a plurality of sensors with respective sensor wavelengths, wherein the sensors are configured such that the sensor wavelength for each sensor in a respective set is substantially equal when the measurand experienced by each of the sensors in that set is equal. The apparatus further includes a detector configured to monitor the light reflected by the sensors, and a control system.

Abstract: A hose to be evaluated is installed on a fixing frame in a preset shape, and a strain gauge and markers are attached to a surface of the hose. During a course of application of predetermined internal pressure to the hose, strain data is acquired using the strain gauge and an image of an external shape of the hose is captured using a camera device to acquire image data. Based on the strain data and the image data acquired, a change in the shape of the hose between a plurality of time points at identical internal pressure is determined. Such hose fatigue resistance evaluation method can determine changes in the degree of deformation of a hose over time due to repeated application of internal pressure.

Abstract: An imaging head 100 includes a laser projector 110, an LED projector 120, a light receiving lens 132, a light receiver 131, and a processor 200. The laser projector 110 emits measurement light to a workpiece W. The LED projector 120 emits uniform observation light to the workpiece W. The light receiving lens 132 converges reflected light of the measurement light and reflected light of the observation light that are reflected back from the workpiece W. The light receiver 131 has a light receiving surface composed of multiple light receiving elements that are two-dimensionally arranged. The laser projector 110, the light receiver 131, and the light receiving lens 132 are arranged so that a plane containing the light receiving surface and a plane containing the principal plane of the light receiving lens 132 will satisfy the Scheimpflug condition relative to a light projection axis of the laser projector 110.

Abstract: The present invention provides an event positioning method, device and application in a distributed fiber vibration monitoring system. When a location at which an event occurs in a sensing fiber is to be positioned, an interference field signal having a maximum optical power is obtained by comparing optical powers of respective interference field signals corresponding to backward Rayleigh scattering lights that are generated when a pulse light is transmitted in the sensing fiber. Subsequently, a sensing location of the interference field signal having the maximum optical power is calculated. Finally, the location at which the event occurs in the sensing fiber is determined, according to the sensing location and a location distribution pattern of the event. According to the positioning method provided in the present invention, by screening the interference field signals and then calculating the event location, the spatial resolution is not determined merely by the pulse width of the optical signal.

Abstract: A method for testing a tire by interferometry in a pressure chamber of a tire testing device includes capturing phase images at different pressures in the pressure chamber, generating partial phase difference images between successive phase images, and summing the partial phase difference images to form an overall phase difference image. The pressure in the pressure chamber is changed in a first direction during a first measurement phase and the pressure is changed in the opposite direction during a second measurement phase, wherein at least one partial phase difference image from the first measurement phase and at least one partial phase difference image from the second measurement phase are included in the summation.

Abstract: A system for classifying objects detected in shearographic images identifying via a derivative peaks method, process, or algorithm is accomplished with a CNN (CNN). The system utilized training techniques of the CNN to classify objects as threats or non-threats. The system utilizes extracted clips from the shearographic image that contain the presence of an object so that the extracted clip containing the object is/are evaluated by the CNN to classify the object on or below a surface that has been insonified or otherwise stimulated to generate the shearographic image.

Abstract: A system and method are used for an optical fiber having a core multiple, closely-spaced optical gratings written along the core that create a repeated pattern in the core. A memory stores predetermined reference reflection data and measurement reflection data determined for a length of the core detected from interferometric patterns corresponding to scatter reflections received from the core. Data processing circuitry reduces or removes from the measurement reflection data information that corresponds to reflections due to the repeated pattern in the core to produce filtered measurement data. One or more portions of the filtered measurement data is/are correlated with one or more portions of the reference reflection data to produce multiple correlation values. The greatest of the multiple correlation values is determined, and a location along the fiber corresponding to the greatest correlation value is identified.

Abstract: Methods of improving the measurement of knee stress in an ion-exchanged chemically strengthened Li-containing glass sample that includes a knee are disclosed. One of the methods includes compensating for a shift in the location of the TIR-PR transition location associated with the critical angle location, wherein the shift is due to the presence of a leaky mode. Another method includes applying select criteria to the captured mode spectra image to ensure a high-quality image is used for the knee stress calculation. Another method combines direct and indirect measurements of the knee stress using the mode spectra from multiple samples to obtain greater accuracy and precision as compared to using either the direct measurement method or the indirect measurement method alone. Quality control methods of forming the glass samples using measured mode spectra and related techniques for ensuring an accurate measurement of the knee stress are also disclosed.

Abstract: A system for monitoring parameters of a sample includes an imaging unit including a lens assembly and a detector unit configured for collecting light arriving from a region of interest on an object while being defocused with respect to the region of interest and generating defocused image data pieces indicative of light collected from the region of interest. The lens assembly includes at least one lens and is configured for defining at least one intermediate optical plane being a conjugate image plane or an intermediate Fourier plane with respect to an image plane of the detector unit. The system includes at least one symmetry replicator located at the at least one intermediate optical plane, thereby providing imaging of secondary speckle pattern on the detector array having a selected symmetry condition.

Abstract: Provided is a method for determining strain change in an optical fiber.

Abstract: A system may be provided for optically testing the integrity of a sealed article such as a lithium-ion battery. The system may include a chamber, a pressurizing apparatus that provides a pressure differential between the interior and exterior of the chamber, and an optical imaging apparatus that detects a change in shape of the article in response to provision of the pressure differential. The optical imaging apparatus may be a shearography device, which may be connected to a computing apparatus that receives images before and after provision of the pressure differential and generates a comparison image indicating the change in shape. The comparison image may be manually or automatically analyzed to determine whether the change in shape is significant, indicating the existence of a proper seal.

Abstract: Local strain and optionally other properties of an optical sensing fiber are detected as a function of position along the optical sensing fiber. A light pulse with a plurality of simultaneous laser modes at mutually different wavelengths is transmitted into the optical sensing fiber. Light produced by backscattering of the light pulse in the optical fiber is fed to a multi-way coupler, via a first and second optical path with different optical path lengths. Intensities of different phase combinations of light from the paths are detected by detectors at the outputs of the multiway coupler. A data processing system computes relative phase values of light from the first and second paths for a series to time points with time delays corresponding to scattering at different positions along the fiber. In an embodiment, inelastically scattered light such as due to Brillouin scattering and/or Raman scattered light is selective passed to the detectors and detected.

Abstract: Exemplary embodiments provide for a method for continuous measurement of displacements profile of building structures and a sensor for implementation of this method for repeated, automatic displacements profile measurements of the medium by means of optical fiber elements. This is of particular relevance in engineering structures, engineering structure elements, geotechnical structures. The apparatus is characterized in that the measurement involves a measuring sensor, which is constructed of a core with coupled optical fiber sensing elements for determining the core strains and an optical fiber sensing element for determining temperature, placed freely in an axial channel of the core, making possible to perform measurements in such a way, which that allows for compensation of the influence of sensor temperature.

Abstract: A number of variations may include a product comprising: at least one sensor comprising an optical fiber comprising a first end comprising a semiconductor material, a second end, and a longitudinal midsection comprising a grating, wherein the sensor is constructed and arranged to provide measurements that derive both state of charge and temperature of an electrochemical device simultaneously.

Abstract: A control valve monitoring system is disclosed. The control valve monitoring system includes at least one sensor connected to one of a valve stem or valve shaft, and the at least one sensor detects a change in mechanical integrity of one of the valve stem or valve shaft. A device for providing data regarding the change in mechanical integrity of one of the valve stem or valve shaft is provided, allowing maintenance of the valve shaft or valve stem to be conducted in an efficient manner.

Abstract: An optical frequency domain reflectometry (OFDR) measurement is produced from an OFDR apparatus that includes a tunable laser source coupled to a sensing interferometer and a monitor interferometer. The sensing interferometer is also coupled to a waveguide, e.g., an optical sensing fiber. Sensor interferometric data obtained by the OFDR measurement is processed in the spectral domain (e.g., frequency) with one or more parameters to compensate for the optical dispersion associated with the sensing interferometer data. A Fourier Transform of the dispersion-compensated sensing interferometric data in the spectral domain is performed to provide a dispersion-compensated OFDR measurement information in the temporal (e.g., time) domain.

Abstract: An optical interferometer (1) is used to determine information about the position, gradient or motion of a surface of an object (2) at each of a plurality of points on the surface. An image is projected onto the surface of the object (2), such that, for each of the plurality of points, the intensity or spectrum of the projected image at that point depends on the determined information about the position, gradient or motion of the surface at that point.

Abstract: A technique facilitates the use and application of a distributed vibration sensing system in, for example, a well application. The technique enables selection of a desired gauge length to achieve an optimum trade-off between the spatial resolution of a distributed vibration sensing/distributed acoustic sensing system and signal-to-noise ratio. The optimum gauge length can vary according to specific factors, e.g. depth within a well, and the present technique can be used to account for such factors in selecting an optimal gauge length which facilitates accurate collection of data on dynamic strain.

Abstract: A signal processing apparatus which has an input for receiving a signal conveying a response from first and second optical components to an optical excitation. The first and second optical components are in an optical sensor which is intended to be placed in a sensing zone. The sensing zone contains hydrogen susceptible to migrate into the optical sensor. The signal processing apparatus has a processing entity for processing the response from the first and second optical components to derive information on hydrogen concentration in the optical sensor.

Abstract: Embodiments can be used to synthesize physically plausible animations of target objects responding to new, previously unseen forces. Knowledge of scene geometry or target material properties is not required, and a basis set for creating realistic synthesized motions can be developed using only input video of the target object. Embodiments can enable new animation and video production techniques.

Abstract: Systems and methods according to one or more embodiments are provided for a flexible and local laser shroud that conforms to a contoured work surface and confines laser light energy from a laser end effector to the work surface. In one example, a system includes a laser end effector coupled to a robotic arm to provide laser light energy to a work surface. The system also includes a shroud coupled to the end of the robotic arm and extending to the work surface. The system further includes, as part of the shroud, a flexible laser light seal to conform to the work surface to substantially prevent the laser light energy from passing between the shroud and the work surface as the laser end effector travels along the work surface.

Abstract: Various embodiments herein each include at least one of systems, devices, methods, and software for overhead camera synchronization, such as with regard to a camera positioned above a POS terminal or other kiosk terminal type. One embodiment in the form of a method includes adjusting at least one of an exposure setting of an imaging device and lighting within a field of view of the imaging device to affect an exposure within an image captured by the imaging device. This method further includes capturing an image with the imaging device with the at least one of the exposure setting of the imaging device and the lighting within the field of view of the imaging device to achieve a desired exposure within the captured image.

Abstract: A fiber optic sensor and related method are described, with the sensor including a cross-coupling element in the optical path between a polarizing element and a sensing element, but separated from the sensing element itself; with the cross-coupling element generating a defined cross-coupling between the two orthogonal polarization states of the fundamental mode of a polarization maintaining fiber guiding light from the light source to the sensing element thus introducing a wavelength-dependent or temperature-dependent sensor signal shift to balance wavelength-dependent or temperature-dependent signal shifts due to other elements of the sensor, particularly signal shifts due to the wavelength dependence of the Faraday effect or the electro-optic effect constant.

Abstract: A system and method for detecting dynamic strain of a housing. The system includes an optical fiber linearly affixed along a surface of a length of the housing and an interrogator comprising a laser source and a photodetector. The optical fiber comprises at least one pair of fiber Bragg gratings (FBGs) tuned to reflect substantially identical wavelengths with a segment of the optical fiber extending between the FBGs. The segment of the optical fiber is linearly affixed along the surface of the housing. The interrogator is configured to perform interferometry by shining laser light along the optical fiber and detecting light reflected by the FBGs. The interrogator outputs dynamic strain measurements based on interferometry performed on the reflected light.

Abstract: The laser speckle interferometric system includes a memory for storing a measurement result of a correction parameter and models for matching a result of processing the speckle pattern to the parameters of the object and a processor for stabilizing the speckle pattern detected by controlling a condition for detecting the speckle pattern in real time, processing a time-varying function representing a temporal change in the speckle pattern based on the speckle pattern and the parameters and generating data indicating tested parameters.

Abstract: Provided is a method and system for dynamic shearographic inspection. The dynamic shearographic method allows nondestructive inspection of layered materials, in particular, those including a porous material. The method uses a load profile that increases and decreases the load, for example in a saw-tooth manner, without decreasing the load back down to the initial loading state, usually zero loading. Using the load profile in this manner constantly refreshes the reference speckle images to minimize background noise and allows defects to be distinguished from the noise.

Abstract: There is described an optical pressure sensor comprising a sensor housing and an optical pressure cell mounted within the sensor housing and dividing the sensor housing into a first fluid space and a second fluid space. The optical pressure cell comprises a front side exposed to a pressure in the first fluid space and a back side exposed to a pressure in the second fluid space. The optical pressure sensor further comprises a fluid communication arrangement allowing pressure equalization between the pressure in the first fluid space on the front side and the pressure in the second fluid space on the back side of the optical pressure cell.

Abstract: The invention relates to a method for the determination, at least in regions, of a contour of at least one additively manufactured component layer, in which a contour line of the component layer is traveled over, at least in regions, by a laser beam, and a time exposure of the traveled contour line is produced by a camera system. The invention further relates to a device for the determination, at least in regions, of a contour of at least one additively manufactured component layer. For this purpose, the device comprises at least one laser system, by which a contour line of the component layer can be traveled over, at least in regions, by a laser beam, and a camera system, which is designed to produce a time exposure of the contour line traveled over by the laser beam.

Abstract: Multiple optical architectures based on photosensitive arrays are disclosed. The optical engines collect five dimensional data from the samples with three dimensional spatial information and temporal and spectral information simultaneously, in parallel from all channels, without optical scanning. The photosensitive arrays and/or last component of illumination system are in contact or close proximity of the sample surface. The application of optical engines to sensitive detection of species of interest in the complex reflecting and scattering matrix with the high concentration of interfering species is described. The optical engines are applicable to noninvasive, mobile monitoring of various species of interest in vivo and in vitro.

Abstract: Both a hologram and fluorescence are simultaneously captured in a state in which they can be reconstructed separately. A recording device (10) includes: a laser light source (LS1) which irradiates a subject (13) with object illumination light so that object light is generated; and an image capturing device (12) which captures (i) a hologram formed by interference between reference light and object light and (ii) an image of fluorescence, and the object illumination light further excites a fluorescent material (14) contained in the subject (13).

Abstract: According to examples, a temperature or strain distribution sensor may include a photodiode to acquire a beat frequency between a first laser beam and a second laser beam. A modulator may modulate the first laser beam that is to be injected into a device under test (DUT). A coherent receiver may acquire a backscattered signal from the DUT, and use the second laser beam as a local oscillator to determine a Brillouin trace with respect to the DUT. The Brillouin trace may be used to determine a Brillouin frequency shift and a Brillouin power for the DUT to implement an absolute referencing of a Rayleigh reference trace. The coherent receiver may determine, relative to the Rayleigh reference trace, a further Brillouin frequency shift and a Rayleigh frequency shift to determine a temperature or a strain associated with the DUT.

Abstract: The present disclosure is generally directed to a strain sensor, system and method of fabrication and use that includes an optical fiber, an optical signal generator that transmits an optical signal through the optical fiber, at least two photonic crystal slabs within the optical fiber separated by a first segment of optical fiber, a photo-detector that detects a reflected optical signal from the at least two photonic crystal slabs, and a processor that computes a mechanical strain over the first segment of optical fiber based on the reflected optical signal detected by the photo-detector.

Abstract: Methods of characterizing ion-exchanged chemically strengthened glass containing lithium are disclosed. The methods allow for performing quality control of the stress profile in chemically strengthened Li-containing glasses having a surface stress spike produced in a potassium-containing salt, especially in a salt having both potassium and sodium. The method allows the measurement of the surface compression and the depth of the spike, and its contribution to the center tension, as well as the compression at the bottom of the spike, and the total center tension and calculation of the stress at the knee where the spike and the deep region of the stress profile intersect. The measurements are for a commercially important profile that is near-parabolic in shape in most of the interior of the substrate apart from the spike.